I've got an idea for a duo pair of characters, one who gets her power from the sun and is bubbly and happy and cheery, and the other who gets her power from the moon, who is a moody depressed goth girl. 

And for some reason nobody has ever seen them both at the same time. 

And they definitely aren't the same person whose powers and personality completely flipflop the moment the sun comes up/goes down. Definitely.